Dispersants containing terminal acidic groups, such as, carboxylic acid (such as derivatives of 1,2,4-benzenetricarboxylic acid), phosphates and sulphates are known for dispersing conventional pigments (i.e., pigments utilized as dispersed particles in a binder and characterized for adsorbing certain wavelengths of visible light and reflecting other wavelengths). The phosphate and sulphates are generally prepared by reaction of a hydroxy terminated polymer chain with phosphorus pentoxide, phosphorus oxychloride, polyphosphoric acid or sulphuric acid. The dispersant polymer chains are often derived from polyester or polyalkoxylate chains containing terminal hydroxyl groups. These dispersants known in the art containing terminal acidic groups are suitable for a polar continuous medium, such as, water, ketones, esters and the like.
Civilizations have made a variety of ceramic articles such as cooking and serving vessels, water and other fluid containers, tiles, bricks, etc., for thousands of years. These were typically coloured or decorated with metal oxide type pigments that developed more intense colours during an elevated temperature firing of the pigment and ceramic article. The metal oxide type colouration pigments were thought to chemically interact and interpenetrate at high temperatures with the ceramic composition and/or with more glassy compositions sometimes applied with the colouration pigments or subsequently applied. The more glassy compositions were often to provide impermeable or barrier properties to the outer surface of the ceramic article (to protect the ceramic article from environmental materials with which it might come in contact).
With conventional organic pigments in polymeric organic binder, the particle size and particle uniformity are very important to get consistent and intense colouration. Inorganic metal oxide pigments for inorganic ceramic colouration are generally not as well understood as organic pigments. The particle size of the inorganic metal oxide pigments generally has not been studied and controlled to the extent that particle sizes of pigments has been controlled for use in polymeric organic coatings and inks. With interest in converting from older printing technologies to digitally printing on ceramic articles using ink jet nozzle technology, there is a need to reduce the particle sizes of inorganic metal oxide pigments to avoid plugging ink jet nozzles.
U.S. 2005/0120911 and U.S. 2008/0033102 disclose polymeric dispersants prepared from a Jeffamine monoamine and 1,2,4-benzenetricarboxylic acid anhydride, and a polyisobutylene amine and 1,2,4-benzenetricarboxylic acid anhydride, respectively. The former agents are used as dispersants on inorganic and organic lake pigments in polar solvents such as ester and alcohols and are not useful in non-polar solvents such as aliphatic mineral oil. The latter agents are used as dispersants in non-polar solvents only and cannot be used in polar solvents.
U.S. Pat. No. 8,167,992 discloses polyether amine based dispersants containing a polar inorganic group. The polar inorganic group includes groups such as a sulphur or phosphorus acidic polar head group.
US 2009/0142526 to Sun Chemical Corp. teaches a dispersant which is the reaction product of at least one dianhydride with at least two different reactants, each of which can be an amine, alcohol, or thiol, and at least one of which is polymeric. The polymeric component is often based on a poly(alkylene oxide) backbone.
U.S. Pat. No. 8,133,914 teaches dispersants comprising poly(alkylene oxide) and aromatic carboxylic acid.
WO2012/107379A1 is directed to a aminic dispersant with poly(oxyalkylenecarbonyl) solubilizing chain and WO2012/116878A1 is directed to ceramic ink for inkjet printers utilizing a dispersant from polyethyleneimine with homo or copolymers based on lactic acid.